Kuroko belongs to the Kuroko tribe and acts as Amano Jyaku's devoted sidekick, harboring profound respect for him. He aids Amano in shielding Tatsuo Nagumo—the human vessel of the Chōjin (Overfiend)—from demonic forces determined to annihilate him. With simian physical traits, Kuroko functions within a core trio alongside Amano Jyaku and Amano's sister Megumi, supporting their mission to protect both Tatsuo and Akemi Ito against incursions from the demon world.